Introduction Variousformer studies have shown that the dentin wall was covered with smear layerafter mechanical shaping of the root canals with instrument (1,2). Disregardingof the controversy over retaining the smear layer it has been recognized that thesmear layer itself may be infected and may protect the bacteria within thedentinal tubules (3). Smear layer not only contains organic components but alsohave inorganic component in the form of dentin chips etc (1). The penetrationof intracanal disinfectants (4) and sealers into dentinal tubules wereprevented by smear layer, which affects the final seal of the root canalfilling (5, 6, 7).

Irrigantsare paramount for complete debridement of the root canals with mechanical procedures(3). There is no single potent solution is appropriate for removing bothorganic and inorganic parts of the smear layer. To eliminate this smear layer mixof sodium hypochlorite (NaOCl) and strong chelating agent such as EDTA (Ethylenediaminetetraacetic acid) isrecommended (8). Crumpton et al.

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proposedthat complete evacuation of smear layer can be achieved by 17% EDTA for 1minfollowed by 5.25% NaOCl (9,12). Till now there is no single solution which candisinfect the root canal system as well as remove the smear layer.

On the otherhand the application of strong chelating agent like EDTA for more than minute and1ml of volume has been reported to be associated with dentinal erosion (10,11).SmearClear(Sybron Endo, Orange, CA) is a product introduced for eliminating the smearlayer. It contains 17% EDTA solution in conjunction with a cationic (Cetrimide)and an anionic surfactant.

SmearOFF (Vista Detal Products) is Proprietary EDTAand Chlrohexidine mix. It is prepared with combination of wetting agents andsurface modifiers for best outcomes. These solutions are used only as finalrinse.Etridonic acid which is soft chelating agent appearsto have a nominal effect on dentine walls and still cut down smear layer.

Lottanti et al.showed that Etridonic acid (HEBP) can be used in combinationwith NaOCl without affecting its proteolytic or antimicrobial properties (13,14). In contrast to EDTA, Etridonicacid is a weak decalcifying agent and hence cannot be used as a mere finalrinse there for it is suggested that HEBP to be mixed with NaOCl to be used asmore complete root canal irrigation solution. Chloroquick(innovationsendo, India) is a combination of NaOCl and HEBP. Chloroquick Highcontains 18% HEBP and 5.

25% NaOCl while Chloroquick Low contains 9% HEBP and 3%NaOCl both be mixed with surfactant tween 80 for complete root canal irrigationsolution. There for this study aims to compare the efficacy of continuous softchelating irrigation protocol with Chloroquick solutions to conventionalirrigation protocol on smear layer removal in coronal, middle, and apicalthirds of the instrumented root canals.  Materialsand methodsSixtyfreshly extracted human premolar teeth with single and straight root canal werepreferred and stored in distal water. Average root length of 12 mm were retainedby decoronating the teeth and then divided into 5 groups (n = 12) randomly. Working length was determined with#10 K-files and deduction of 1mm was done from recorded root length.

Conventionalirrigation protocol was pursued for three groups. After using each file andbefore proceeding to the next canals were irrigated with 2 ml of 5.25% NaOCl.

After instrumentation, all teeth underwent final irrigation as follows:-Group A(control, EDTA) –1ml of 17% EDTA for 1 minute followed by 3 ml of 5.25% NaOCl.Group B (Smear Clear)–1 ml of Smear clear (Sybron Endo, Orange, CA) for 1 minute followed by 3 ml of5.25% NaOCl.Group C (Smear OFF) –1 ml of Smear OFF (Vista dental,) for 1 minute followed by 3 ml of 5.25% NaOCl.

Continuoussoft chelating irrigation protocol was followed for 2 Groups. Group D- ChloroquickLow (innovationsendo) and Group E – Chloroquick High  (innovationsendo). After use of each filecanal was irrigated with 2 ml of respective Chloroquick solution. Afterinstrumentation, all teeth underwent final irrigation as follows:-Group D (Chloroquick Low)- 1 ml of Chloroquick Low solution (9%HEBP + 3%NaOCl)  for 1 minute and final rinse with 3 ml samesolution. Group E (Chloroquck High)– 1 ml of Chloroquick High solution (18%HEBP + 5.25%NaOCl) for 1 minute andfinal rinse with 3 ml of same solution. In-between solutions, 5 ml of distilled water wasused for rinsing canal walls and solutions were introduced with the help of a30-G side vented needle (innovationsendo), which penetrated within 1 to 2 mmfrom the working length.

In the end 5ml of distilled water were used to rinseroot canal walls which were dried with paper points.In the end of entire procedure, two longitudinalgroves were prepared with the help of diamond disc without cutting into thecanal. Grooves were prepared on the buccal and lingual surfaces of each root.

Chisel was used for splitting the teeth. Then the specimens were mounted on themetallic stubs and investigated under a scanning electron microscope (FEIQuanta 200 FE-SEM MK2, Netherlands). Images were obtained at 2000× magnificationsat coronal (9 mm to apex), middle (6 mm to apex), and apical (3 mm to apex)third of each specimen. Scoring criteria was given by Torabinejad M, KhademiAA et al. where scores were given as follow score 1 = no smear layer; all tubules were clean and open and smearlayer was absent on the surface of the canals; score 2 = moderate smear layer; smear layer was not present on thesurface of the canal, but debris were present in tubules; score 3 = heavy smear layer; the debris were observed in tubules andsmear layer enclosed the dentin wall surfaces.An endodntist who was unaware of groups and codingevaluated and scored all the images to exclude observer bias.

Repeatedevaluation was done to ensure intra-examiner consistency.    RESULTSDescriptivestatistics were expressed as numbers for each group. The efficacy of variousagents for smear layer removal was assessed by comparison of groups usingKruskal Wallis ANOVA and Mann- Whitney U test. In the above tests, p value lessthan or equal to 0.05 (p?0.05) was taken to be statistically significant. Allanalyses were performed using SPSS software version 17.

The results for smearlayer scores in each group at coronal, middle and apical are conferred in Tableno 1, 2 and 3. The examination of the surface of root canal walls at coronalthird groups showed less or no smear layer (Fig. 1) and there was no statistically significantdifference (p_0.643).Mostsamples at middle thirds shows no smear layer or minimal smear layer present(Fig. 2) and there was nostatistically significant difference at middle layer of root canals (p_0.

615). Chloroquick High group showed better smear layer removal at the apical thirds (Fig.3). Chloroquick High shows statistically significantly better(p_0.

029) as compared to the other groups. Mann-Whitney U test shows thatChloroquick High is able to remove better smear layer compared to ChloroquickLow (p_0.028).

Choloroquick Low has similar chelatingability as compared to other solution there is no statically significantdifference at apical third.  DISCUSSIONThis examination provides the insightfulunderstanding of smear layer abolition proceeding and capability ofconventional irrigation protocol and continuous soft chelating irrigationprotocol. Satisfactory irrigation, disinfection, and obturation are mainprinciple of shaping. Accumulation of smear layer is noticed while shaping of canalswhich need to abolish with the help of irrigating solution.

Whole activity neededfrom an irrigant to reduce smear layer from dentin wall cannot be obtain by anysole irrigating solution. Therefore, combined application of multiple irrigatingsolutions is obligatory for optimal abolition of smear layer (5).Whereas Chloroquicksolution is mix of HEBP (a soft chelating agent) and NaOCl which can disinfectroot canal as well as reduces smear layer. Highlight of such combination ofNaOCl and Etridonic acid is that the NaOCl doesn’t surrender its biological,antibacterial and tissue dissolving properties (13, 14), whereas the reductionand elimination of the inorganic element is done with help of HEBP (11, 12). Outcome of this current research demonstrate eradicationof smear layer was more decisive in middle and coronal third in comparison toapical third.

These results are in accordance with study done by Abbott PV, Heijkoop PS et al. and numerous studies, which have proved in past thatan effective cleaning action in the middle and coronal third of the root canalseven with numerous irrigation solutions, different volume, and time (15, 16).In coronal and middle third areas where a larger canal diameter allows betterflow of solution and more time to be in contact with dentine wall which allows thesolution to remove smear layer comprehensively. (3,16).            Roleof surfactant has been discussed and reviewed by numerous authors, in currentstudy SmearClear, SmearOFF and Chloroquick contains surfactant. Abou-Rass andPatonai confirmed that reduction of surface tension of endodontic solutionsimproved their flow into slender and narrow root canals (17). Therefore, animproved penetration into apical narrow part of canals can be seen withaddition of surfactants to irrigation solution.

In present study, SmearClearand SmearOFF despite having additional surfactant doesn’t show the significantremoval of smear layer in apical third when compared to control group of 17%EDTA, which does not have any addition surfactant. This result is in accordancewith the observations of Lui et al. (18) and also, other studies have shownthat calcium chelating ability of solution is not improved by reducing the surfacetension of the solution.             Presentstudy results display that the continuous softchelating irrigation shows the significantly better removal of smear layer thanconventional irrigation protocol at apical third level when 18% HEBP was usedin combination with 5.25% NaOCl (Chloroquick High). Where 9% HEBP incombination with 3% NaOCl (Chloroquick Low) did not show any significancedifference compared to conventional irrigation protocol groups.

These results canbe attributed to chelating agent being more time in canal and also chelatingprocedure is seen while instrumentation, unlike conventional irrigationprotocol where removal of smear layer is done only once instrumentation iscompleted (19). Paque et al. demonstrated that the accumulation of hard tissuedebris in root canals when irrigated with amalgamation of  sodium hypochlorite and etradonic acid wassignificantly less than irrigation was performed with 2.5% sodium hypochlorite alone(20).Another advantage of this combination is that it has better tissuedissolution capacity by keeping the hypochlorite-hypochlorous acid equilibriumtowards hypochlorite (21). This combination is affective on inorganic as wellas organic part of smear layer at same time.            Resultof this study is in contrast to the recently published research by AbyKuruvilla et al.

where 7%malic acid wassignificantly efficient in abolishing smear layer as compared to 17% EDTA and18% etidronic acid (22). This observation may be seen because 18% etidronicacid which is soft chelating agent was merely used in a final rinse irrigationprotocol and not combined with sodium hypochlorite. There arevery few studies available on use of the continuous soft chelating agent forsmear layer removal. Future study should be aimed towards effect of both thisprotocol on root canal walls. In present study, continuous soft chelatingirrigation protocol shows promising results.CONCLUSIONWithin the constraint of this in-vitro study boththe protocols conventional as well as continuous soft chelating irrigationprotocols were able to remove smear layer at coronal and middle third of the rootcanals but at apical third continues soft chelating irrigation protocol accomplishedwith Chloroquick High (18%HEBP) shows better removal of smear.